Methods.Electrons are traced in linear force-free magnetic fields extrapolated
from SOHO/MDI magnetograms, endowed with anomalous resistivity (η) in localized
dissipation regions where the magnetic twist exceeds a given threshold.
Associated with is a parallel electric field that can accelerate
runaway electrons. In order to gain observational predictions, we inject electrons inside the dissipation
regions and follow them for several seconds in real time.

Results.Precipitating electrons that leave the simulation
system at height are associated with hard X rays, and electrons that escape at height km are associated with normal-drifting type IIIs at the local plasma frequency. A third, trapped
population is related to gyrosynchrotron emission. Time profiles and spectra of all three emissions are calculated,
and their dependence on the geometric model parameters and on η is explored. It is found that
precipitation generally precedes escape by fractions of a second and that the electrons perform many visits to
the dissipation regions before leaving the simulation system. The electrons impacting reach
higher energies than the escaping ones, and non-Maxwellian tails are observed at energies above the
largest potential drop across a single dissipation region. Impact maps at z = 0 show the tendency
of the electrons to arrive at the borders of sunspots of one polarity.

Conclusions.Although the magnetograms used
here belong to non-flaring times, so that the simulations refer to nanoflares and
“quiescent” coronal heating, it is conjectured that the same process, on a larger scale,
is responsible for solar flares.

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